1. Field of the Invention
The invention relates generally to the field of laser diodes and more generally to laser diode feedback light detector combinations for use therein.
2. Brief Description of the Prior Art
Laser diodes have many applications. One of these is in optical disk drives. Optical disk drives are typically composed of several subsystems. Among these are a laser light pen 10 and its power control 22, 24. FIG. 1. The laser light pen 10 in turn typically comprises a laser diode 12, and a feedback light detector 18 for the purpose of monitoring the light power output of the diode.
The current developed by the detector 18 in conventional pen apparatus varies from laser diode to laser diode due to various factors, among these are the large beam dispersion angle from the laser diode rear facet 14 and mechanical tolerances in the pen optics. Conventional power control circuits compensate for these variations by providing calibration potentiometers 24, 26. As the laser diode in optical disk drives may be operted at two power levels, i.e., a read level and a write level, two corresponding potentiometers 24, 26 are provided.
When, as is sometimes the case, a laser diode wears out or otherwise malfunctions, the laser light pen is replaced as a unit. This necessitates a technician recalibrating the set points on two potentiometers, which may be a time consuming task. The procedure must be repeated each time the laser pen must be replaced.
Elimination of the recalibration step could not only save valuable time when a laser light pen must be replaced, but could also eliminate the need for a technician altogether.